The resultant end or by-product of flue gas desulfurization (FGD) is often a gypsum slurry. Impurities that enter the FGD system with the flue gas, reagent, make-up water, etc., subsequently translate to varying levels of contaminants present in the gypsum slurry. It is desirable to purify this gypsum slurry by reducing the contaminants therein. Such a purified product has greater commercial worth due to the reduction of undesirable contaminants such as flyash, unburned carbon, limestone impurities, and ultra fine particulate that adversely effect its end use in industries such as the manufacture of wallboard. In terms of disposability, a purified end product results in less disposal cost or liability due to a reduction in impurities which, if not removed, can provide sources of leachable metal.
It is an object of this invention to utilize hydroclones to selectively remove undesirable constituents, in the form of fine solids, from the FGD end product. Additionally, with these contaminants removed, downstream clarifiers, press filters, and/or other dewatering devices can be used to further concentrate the undesirable solids stream so that these solids can be eliminated without also discarding any salvageable process return water. As far as is known, such use of a hydroclone is not known to exist for the purpose of purifying the FGD gypsum slurry end product.